1. Field of the Invention
This invention relates to balloon catheters for medical use. More particularly this invention relates to shape control of an inflated medical balloon catheter for specialized medical applications such as valvuloplasty and other dilating procedures.
2. Description of the Prior Art
Balloon catheters have long been used to expand hollow viscera and vascular channels. In medical applications, where an unknown, possibly variable resistance opposes the inflation of the balloon, fine control of the shape and size of the expanded balloon is desirable in order to avoid excessive deformation or the subject and more the more serious complication of rupture. In certain applications shape control is desirable to prevent axial displacement of the balloon during the dilation procedure.
This problem is addressed in Inoue, U.S. Pat. No. 4,327,736, wherein it is disclosed to apply a relatively broad rubber band about a middle portion of the tube, to restrict expansion thereof. When finally inflated, a "waist" forms in the mid portion in accordance with the differential resilience in the middle portion and the end portions of the balloon. The resultant shape is well adapted to valvuloplasty procedures, as the balloon is inhibited from slipping off the valve.
in another approach disclosed in the above noted Inoue patent the balloon is composed of two rubber layers and a cloth web or net therebetween. The relatively unyielding cloth serves to limit the size of the expanded balloon.
Both these approaches complex structural elements and are expensive and cumbersome to produce, particularly in a variety of shapes and sizes as may be medically desired.